GLOSSARY – N-O

GLOSSARY – N-O

NAPPE
A sheet of rock that has moved sideways over neighboring strata as a result of an overthrust or folding.

OORT CLOUD
Cloud of comets hypothesized to be the source of the long-period comets. Periodical disturbance of the Oort cloud has been proposed to be related with a disputed periodical increase of cometary impacts on the Earth (Shiva theory).

Visual representation of the Oort Cloud, which is littered with ice and rocks left over from the formation of the Solar System. (Image: NASA) The Oort Cloud is an extended shell of icy objects that exist in the outermost reaches of the solar system. It is named after astronomer Jan Oort, who first theorised its existence. The Oort Cloud is roughly spherical, and is thought to be the origin of most of the long-period comets that have been observed.

OXYGENATION EVENT
2.4 billion years ago, the irreversible increase in the oxygen content of Earth’s near-surface atmosphere. Not only did it affect biological survival on our planet, but it also resulted in an extraordinary increase in mineral diversification.